Field of the Invention
The present invention relates to an apparatus for applying a surface pressure to progressively moving workpieces such as chipboard panels. In a known apparatus for applying a surface pressure, there is provided at least one rotating belt adapted to be pressed against the workpiece by a pressure medium. The pressure medium is introduced into a pressure chamber sealed by a sealing member adjacent to the belt. The sealing member is guided by a frame or holder in a groove formed in a pressure plate. The belt is in sliding engagement with, and slides along, the sealing member.
In such a known apparatus, the width of the frame or holder has hitherto been selected so as to be as large as the width of the groove, so that the frame fits into the groove. The frame is inserted into the groove in the absence of pressure and is pressed out therefrom by means of the pressure medium introduced into the interior of the groove. Whilst the pressure medium for example, compressed air, urges the frame, and the sealing member associated therewith, in a vertical direction towards the surface of the belt, the compressed air contained in the pressure chamber acts against the lateral surface of the belt and produces a force directed parallel to the surface of the belt. This force produces a moment acting on the frame or holder causing tilting of the frame within the groove. If the frame is tilted, it therefore cannot be displaced relative to the pressure plate by means of the compressed air. A result of such effect is that if the belt deviates from the plane of its direction of travel during the pressing operation, the sealing member cannot follow these deviations so that a gap appears between the belt and the sealing member. The compressed air may be discharged from the pressure chamber through this gap and the sealing member cannot, therefore, fulfil its object.
The present invention seeks to provide an apparatus of the general type described above but which ensures, in use, constant abutment of the sealing member against the pressure application belt sliding therealong but which permits unobstructed movement of the sealing member and the frame associated therewith in a direction at right angles to the plane of movement of the belt if the band deviates from its plane of movement.
In accordance with the present invention, there is provided an apparatus for applying a surface pressure to progressively moving workpieces such as chipboard panels comprising at least one rotating pressure application belt having a workpiece-carrying surface and an opposed surface and means for applying pressure to said belt to cause said belt to apply pressure to said workpiece said pressure application means comprising a sealing strip in sealing abutment with said opposed surface of said belt, said sealing strip together with said belt forming part of a pressure chamber into which a pressure medium is induced, guide means for guiding said sealing member, said guide means comprising a pressure plate, said pressure plate having a recessed wall portion formed therein to define a groove, said groove receiving a frame member, said frame member guiding said sealing member, the improvement comprising dimensioning said frame to be smaller than said groove such that a spacing is maintained therebetween, a resilient sealing member spanning said spacing, said resilient sealing member having a first end and a second end, said first end portion connecting said resilient sealing member to said frame and said second end portion slidingly abutting said recessed wall portion defining said groove.
Preferably, said frame has an end portion facing said pressure belt, said apparatus additionally comprising a plurality of retaining yokes, said yokes projecting into the region of said groove and laterally supporting said end portion of said frame.